1. Field of the Invention
This invention relates in general to certain new and useful improvements in an apparatus and method for producing fiber reinforced plastic composite articles which may have non-uniform shape and/or volume, or both, over their length, and more particularly, to such articles as well as apparatus and method of the type stated for producing such articles which may have a non-uniform cross-sectional shape and/or volume over their length utilizing a plug of moldable material surrounded by a curable binder impregnated reinforcing material.
2. Brief Description of the Priot Art
In recent years, reinforced plastics have achieved substantial prominence and have found applications in many areas which were previously satisfied by products fabricated of heavy metal and other similar structural materials. Furthermore, improved raw material prices and increased availability of reinforced platic materials have favored the use of reinforced plastic materials and the production of various reinforced composite plastic objects over those fabricated from heavy metals and other similar structural materials.
With the increased use of reinforced plastic objects, there has been the attendant availability of many apparatus for winding filament containing strands about mandrels in order to produce various forms of reinforced plastic objects. One such filament winding system is taught in U.S. Pat. No. 3,740,285, dated June 19, 1973 to William Brandt Goldsworthy et al for winding filament containing strands about a rectangularly shaped mandrel. Another form of filament winding apparatus is more fully illustrated and described in U.S. Pat. No. 3,769,127 dated Oct. 30, 1973 by William Brandt Goldsworthy et al, for winding reinforced plastic composite strands about a hollow tubular mandrel in order to produce pipe forms.
In addition to the above, many pultrusion type apparatus have also been provided for pultruding reinforced plastic objects in the forms of bars, tubes, and other profile forms. The conventional pultrusion apparatus is somewhat analogus to extrusion in that the pultrusion apparatus operates continuously to produce constant-section shapes and profiles which are generally formed of reinforcing fibers impregnated with a hardenable binder, such as a resin matrix impregnated in the reinforcing fibers. The resin impregnated fiber reinforcing material is essentially pulled through a shaping and forming die in a generally linear path by one or more puller mechanisms.
Pultrusion apparatus of this aforementioned type are more fully illustrated and described in U.S. Pat. No. 2,871,911, dated Feb. 3, 1959, to William Brandt Goldsworth et al and in U.S. Pat. No. 3,556,888, dated Jan. 19, 1971 to William Brandt Goldsworthy. In addition, there has been a pultrusion apparatus which is capable of producing objects which are non-linear over their length, as for example, that apparatus described and illustrated in U.S. Pat. No. 3,873,399, dated Mar. 25, 1975 to William Brandt Goldsworthy. However, in each of these cases, the object which was produced has a relatively constant cross-sectional shape and clearly had a relatively constant cross-sectional volume.
There has also been commercially available apparatus for producing resin impregnated fiber reinforced composite materials which are maintained in an A-stage, namely, a stage in which the resin material is not cured, as for example, in U.S. Pat. No. 3,650,864, dated Mar. 21, 1972 to William Brandt Goldsworthy. This apparatus received a conglutinate mass containing resin impregnated fiber reinforced strands which were wrapped in a plastic film and retained for further use at which time the resin impregnated mass could be ultimately cured and bent into a desired shape. However, this apparatus did not produce any final hardened article of non-uniform shape across its length on a continuous basis.
Heretofore, there has been no commercially available apparatus which utilizes filament winding techniques or pultrusion techniques or even, extrustion techniques capable of producing a reinforced plastic composite object of non-uniform shape across its length. In many of the conventional filament winding apparatus, and many of the conventional pultrusion apparatus, the production quality is not constant, and these apparatus often produce stock of both structurally and aesthetically inferior quality, resulting in a high scrap loss.
In the case of the pultrusion apparatus, one of the major causes of poor quality and subsequent rejection of the finished pultruded article, results from the sloughing of the material forming the article which is created by frictional forces within the shaping and forming dies forming part of the pultrusion apparatus. These shaping and forming dies shear the outer resinous surface of the moving composite materials to thereby create an object of poor quality, inasmuch as the sloughing causes pieces of cured resin or a resin reinforced composite to stick to the die tube surface.
Other problems which have arisen in connection with both conventional pultrusion apparatus and conventional filament winding apparatus, is that of curing the reinforced plastic composite as it moves through the forming system. Conventional conductive heating and similar forms of heating or curing were found to be satisfactory in effecting a cure of the resin matrix when relatively small diameter profiles in relatively thin cross-sectional shapes were formed. However, in recent years, newer applications for these products have given rise to a requirement for articles, whether or not pultruded, or filament wound, which are of a fairly thick cross-sectional area. This requirement has posed a need for some effective forming of the object in the initial state and curing of the object in the final process when the object was in the desired cross-sectional shape over its length. Notwithstanding, in all prior art apparatus it was necessary to substantially reduce the "running" rate of the material passing through the apparatus in order to produce an object of the desired shape and size.
In recent years, it has been found that there is a substantial demand for reinforced plastic composite articles in the form of handles e.g. hammer handles, ax handles and like objects. However, there has been no effective commercially available device which is capable of producing these articles from reinforced plastic composite materials where the shape of these articles may not be uniform in either shape or volume or both along their length. Consequently, conventional filament winding apparatus and conventional pultrusion apparatus are not capable of producing such articles on a continuous mass production basis. Thus, many articles of this type have been produced of conventional materials such as wood or the like. The present invention obviates these and other problems through the provision of an apparatus and method which are capable of producing reinforced plastic composite articles which may have a non-uniform shape and/or a non-uniform material volume along their length.